*2.1.2. Nonusage of local antigens*

Some of the viral diseases of poultry like infectious bursal disease and salmonella have many serotypes. Some of the serotypes are prevalent in one area, while others are prevalent in other areas. The local disease causing agents in any area are of prime importance for vaccine manufacturing. The strains of viruses differ from area to area. The local serotypes and locally isolated antigens are considered the most suitable immunogens for formulating vaccines. The nonusage of local vaccine antigens may result in disease outbreaks [2]. The foreign vaccine may be made from serotypes that are different from field strain [12]. Moreover, vaccination with foreign vaccine may not provide immunity to birds if the field strain is of higher virulence and of a different nature [13].

#### *2.1.3. Improper storage temperature*

After the formulation of the vaccine, its storage is of utmost importance. The freeze-dried vaccines require freezing temperatures, while lyophilized vaccines may be stored at 4°C, and during transportation the low temperature might not be properly maintained. The Marek's disease vaccine is stored in liquid nitrogen at very low temperatures, while live vaccines of ND, IBD, IB, etc. are stored at 4–8°C. The oil-based vaccines may be stored below 8°C. In the poultry sector, almost all the vaccines available are thermolabile in nature. The maintenance of proper cold chains and storage temperature is a prerequisite for optimal potency of vaccines. The shortage of electricity, weak, nonfunctional, obsolete and repaired storage equipment, high temperature during transport, refrigerators without thermometers, etc. are the common problems of vaccine storage of developing countries like Malaysia, India, Tanzania and Pakistan [14–18]. Data have been recorded about use of vaccines after purchase from the market in Nigeria, and it has been found that 16% of farmers do not perform vaccination on the date of purchase of vaccine and 7% of farmers store the vaccine on the shelf without proper preservation, thus resulting in vaccine failure [2].

#### *2.1.4. Exposure to direct sunlight*

It has been documented that vaccines are transported like ordinary drugs [2]. Direct sunlight has UV radiations which are lethal for live viruses. The exposure of vaccine to direct sunlight results in the killing of antigens present in the vial, and as a result, the number of viral antigens is reduced in the vaccine and the vaccine may become ineffective.

disease condition may also contribute to vaccine failure. When the birds are morbid due to the same disease for which vaccination had been done, then there will also be vaccine failure because the antibodies produced against the pathogenic agent will neutralize the antigen of vaccine and a reaction may take place in the body of birds and vaccination may worsen the

Preventing Vaccine Failure in Poultry Flocks http://dx.doi.org/10.5772/intechopen.79330 83

Certain diseases are immune-suppressive in poultry flocks like mycotoxicosis, infectious bursal diseases (Gumboro), chicken infectious anemia, Marek's disease, etc. These immune suppressive diseases may also lead to vaccine failure. The fungal toxins present in poultry feed have a bad effect on the feed conversion, growth, health and immune status. The fungal toxins cause the following effects: carcinogenic, allergic, hypersensitivity and depression. The common age of infection of infectious bursal disease (Gumboro) in poultry flock is at 3rd to 7th week of age. The bursa is a lymphoid organ in poultry where maturation of B cells takes place in poultry. The infection of IBD during this stage of age may lead to permanent damage to bursa; as a result, the maturation of B Cells may not take place in birds throughout their life

span and thus the birds remain prone to vaccine failure during the rest of their lives.

age of the bird is very important at the time of vaccination.

*2.2.5. Interaction with maternal antibodies*

*2.2.6. Improper route of administration*

The receptors for some antigens develop in the body with advancing age. Some of receptors of virus develop as early as with the hatch of a chick. The receptors of diseases like Newcastle disease, infectious bronchitis, etc. develop at a very early age while the receptors of diseases like infectious bursa disease, fowl pox, etc. develop late in the body. Vaccination at a very early age before the development of certain receptors may also result in vaccine failure. The

The antibodies of certain viral diseases are transmitted through eggs. As the breeder/parent flocks of poultry are routinely vaccinated against viral diseases which are prevalent in the area, the newly hatched chicks have maternal antibodies in their blood and these can interact with vaccine antigens. The antibodies against ND virus and IBD virus are transmitted in eggs and provide protection to the newly hatched chicks during the first week of birth. High maternal antibodies interfere with multiplication of live vaccines and reduce the level of immunity production in the chicks. The use of live vaccines during the first week of birth in chicks against diseases whose maternal antibodies still persist in the body of the chick will result in neutralizing of antigen and active immunity may not be provided by the vaccine [22].

The vaccines have specific routes for their administration in the body of the bird, that is, through oral, subcutaneous (S/C), intramuscular (I/M), wing web (W/W), drinking water (D/W), eye dropping (E/D), spray, etc. Not following f specific recommended routes of

condition of disease.

*2.2.4. Immaturity of birds*

*2.2.3. Immunosuppressive diseases*
